Urban bushland has health benefits beyond being a great place to go for a walk. It filters our air and water, helps cities avoid extremes in temperatures, and is linked to lower rates of chronic disease.

But these and other health benefits are virtually never accounted for in local and state land development processes.

Urban planners need to consider these health benefits when making decisions about the future of our cities.

What do we mean by urban bushland?

Urban bushland ranges from a bush park of native trees, to wetlands – in fact any native vegetation characteristic of the local region. With its undisturbed soils and associated wildlife, urban bushland is more diverse than other types of green spaces in our cities, like parks. So it adds significantly to neighbourhood biodiversity.

The more unfragmented the landscape, or unaltered the bushland, the more likely it will be to retain its biodiversity. Hills, watercourses and gullies, or a mixed forest, have greater biodiversity than flat land or a plantation of trees. Landscapes that change by the season add to that diversity.

In cities, health benefits work at two levels. Not only do local residents receive health benefits when they use urban green spaces, the wider urban population also feels the health effects.

Healthy locals

The closer residents live to green space, particularly if it is accessible or usable, the better they report their health.

For an individual, access to green spaces contributes in multiple ways: it reduces stress, it helps us recover from illness or injury, and our thinking abilities improve when we are more contemplative and mindful of our green surroundings.

The quality of green spaces plays a role in the health benefits for locals. For example, views of diverse vegetation more effectively lowers stress compared with less-diverse vegetation.

Exposure to biodiversity from the air, water, soils, vegetation, wildlife and landscape, and all the microbes associated with them (the sort retained in uncleared bushland and wetlands) enhances our immunity. This is thought to be the key to the health benefits of nature.

A recent review highlights the host of physical health problems that are reduced in urban areas with more nature, including less heart disease, obesity and diabetes. Mental health is also improved in urban areas where people are living with more green space.

Urban bushland, like this in the Western Australian city of Joondalup, provides health benefits to locals who access it and the wider population.Author provided

Urban bushland improves city water. Wetlands and the vegetation around them clean our water by filtering, reducing exposure to pollutants carried in groundwater or surface water run-off.

Shrinking urban bushland

Where new suburbs are developed on the outskirts of cities, the end result is usually near-complete clearing. Urban bushland is replaced with smaller, fragmented, more sanitised, open and neat spaces.

These are designed for a narrower (but still important) set of usable attributes, like a bike path, lawns and a playground. But the original values of the bushland are lost. This pattern is repeated in the expanding suburbs of cities across Australia.

If some urban bushland, wetlands or other landscape assets have been retained, the pressure on them from development is relentless, as seen recently in Western Australia where a highway is due to be extended through the Beeliar Wetlands.

Planning for better planning

Planning processes need to use ways to assess what we might lose and what we might gain from clearing bushland.

This could involve asking what types of services existing bushland provide for local residents and the city in general. These will include their role in providing clean air and water, controlling floods, cycling nutrients, as well as their recreational or spiritual services.

These could be compared with services the proposed development offers. The comparison should make decision makers, and more importantly the public, better able to judge the true worth or cost of a development.

Such cost-benefit analyses are usually used somewhere in planning processes but rarely, if ever, are the values of biodiversity and ecosystem services considered, or the cost savings from health benefits of bushland.

These sorts of cost-benefit analyses can also be used to account for the health effects associated with local bushland. Such health assessments (or health impact assessments) need to be more widely used. And where land subdivision, road building and suburban housing developments are planned, health assessments may need to be compulsory to better account for the contribution of urban bushland to health.

Urban residents naturally want to stay cool. Air conditioning is the usual choice, but it can be expensive to run. Air conditioning also adds carbon pollution, creates noise and can make outdoor spaces hotter.

So what else can we do to manage increasing urban heat? And who has the ability to act?

Urban planners are increasingly involved in developing and delivering urban greening strategies. While it seems like a “no brainer” to green cities, our international research shows that planners are not always comfortable with this idea.

However, green infrastructure – including street trees, green roofs, vegetated surfaces and green walls – is emerging as a viable way to help cities adapt to increased heat. Uptake of these technologies is slowly increasing in many cities around the world.

Green walls cooling a building in Singapore.Tony Matthews

The Australian government has recognised this trend. An agenda to green Australia’s cities is now in place. Stated aims include managing climate change impacts, reducing urban heat, improving urban well-being and increasing environmental performance.

Benefits of urban greening

The broadening appeal of green infrastructure is helped by the fact it offers multiple benefits.

For example, shading from strategically placed street trees can lower surrounding temperatures by up to 6℃, or up to 20℃ over roads. Green roofs and walls can naturally cool buildings, substantially lowering demand for air conditioning. Green infrastructure can also provide habitat for wildlife, recreational opportunities for people, better management of stormwater runoff and improved urban aesthetics.

Hard surfacing, including concrete, asphalt and stone, is common in cities. It can increase urban temperatures by absorbing heat and radiating it back into the air. Green infrastructure can minimise this difficulty as it better regulates ambient air temperatures. Foliage allows local cooling through evapotranspiration, where plants release water vapour into the surrounding atmosphere.

Why planners are cautious

Our research examined urban planners’ attitudes towards green infrastructure use in Australia, England and Ireland. We found that planners are broadly aware of green infrastructure as an urban intervention. They understand its use, application and capacity to provide multiple benefits, especially in terms of managing urban heat.

The planners we interviewed, while recognising the potential value of green infrastructure, strongly cautioned that delivering the technology can be an uncertain process. The biggest barrier cited was that planning departments are not experienced with green infrastructure.

Put simply, they tend to avoid it because it has not traditionally featured on planning agendas. Like any new planning endeavour, green infrastructure can create institutional, legal, economic, social and environmental challenges.

Some of the biophysical challenges associated with green infrastructure delivery are novel. Choosing appropriate forms of vegetation, for example, may be difficult. Decisions must be made based on prevailing climactic conditions, drainage capacity and species growth patterns.

Will root systems damage buildings or underground utility networks? Might trees topple during storms and damage houses? Are roofs strong enough to support a rooftop garden? Planners may not be able to answer these questions, which creates a need for external experts to advise them.

Our findings also highlight socio-political factors as barriers. These include governance concerns such as the political context in which planning decisions are made.

Management issues also feature. Chief among these are government commitments to budget for green infrastructure delivery and management.

Planners are also wary of public involvement. They know that public sentiment about green infrastructure can be influenced by perceptions of modified access, changed use, or loss.

What can be done?

The urgency for providing urban green infrastructure increases as climate change makes our cities hotter. Our research suggests the principal task for planners is to overcome embedded practices and to accept green infrastructure as an emerging but permanent urban feature.

This will not be easy. For example, a decision to use a road easement for green infrastructure may require multiple meetings with other government departments, utility companies and residents. Planners will need to coordinate these, manage stakeholder expectations and ensure cost sharing where necessary.

Legal, economic, social and environmental issues will require innovative solutions.

Planners will increasingly be tasked to deliver green infrastructure in cities. They will need to be clear on its value, be prepared to lead its delivery and learn from new challenges and solutions encountered along the way.

Urban residents all over the world stand to benefit if planners can successfully meet this challenge, particularly as hotter temperatures threaten urban comfort and habitability.